Just put together a Ceriatone Overtone and have an issue, seems to be a little more technical expertise on this board so I thought I would post here as well as the Ceriatone board.
With no power tubes inserted my B+ plate supply is 420v or so. In this condition, the preamp circuitry works as expected, the signal @ the preamp out is clean and all is good with the world.
Inserting the power tubes (biased as off as possible) drops the plate B+ to 330v or so and there is what looks like modulated power supply hum in the OT output signal. Signal level and controls do not alter the hum content in any way.
I have tried a couple different pairs of 6L6s, they both behave the same.
Any thoughts?
Thanks in advance!
